6. Abstract The overall aim of this project is to determine the mechanisms and long-term consequences of estrogen on mitochondrial function and metabolism in brain. Our target outcome is sustaining mitochondrial function to sustain neurological health for prevention of neurodegenerative diseases associated with aging and mitochondrial dysfunction. Results of our previous mechanistic analyses indicate that 17-estradiol (E2) protects against dysregulation of mitochondrial calcium homeostasis, enhances mitochondrial function, increases efficiency of oxidative phosphorylation, protects against oxidative damage and regulates the mitochondrial proteome. In this project, we are testing the global hypothesis that E2 sustains mitochondrial function to promote the energetic capacity of brain mitochondria by maximizing aerobic glycolysis (oxidative phosphorylation coupled to pyruvate metabolism). As a corollary to this hypothesis, we propose that in the female brain, E2-induced enhancement of mitochondria oxphos-coupled glycolysis can prevent decreased glucose utilization characteristic of aging and delay its expression in a female mouse model of Alzheimer's disease (AD). To test these hypotheses, in Specific Aim I we will determine the functional consequences of long-term E2 regulation of key enzymes required for aerobic glycolysis and oxidative phosphorylation in brain, the cellular selectivity of E2 regulation of mitochondria in primary neurons and astrocytes and impact of loss of ovarian hormones and E2 on brain metabolism using microPET imaging. In Specific Aim II we will investigate the estrogen receptor subtype and signaling mechanisms whereby E2 induces integrated regulation of the mitoproteome and mitochondrial function. In Specific Aim III we will determine the E2-induced signaling pathway(s) that regulate brain mitochondrial function by investigating (1) the role of estrogen receptor subtypes, the obligatory role of the (2) src/MAPK/CREB and (3) PI3K/Akt pathways and (4) nuclear versus mitochondrial site of action in the E2-induced regulation of the functional mitoproteome. In Aim III, we will determine the therapeutic efficacy of E2 to sustain mitochondrial function and brain metabolism during aging and reproductive senescence, ovarian hormone deprivation in a mouse model of Alzheimer's disease. Results of these discovery efforts will advance our knowledge of estrogen action in brain mitochondria and its impact on development of neurodegenerative pathology. Further, these analyses will generate insights into early events that lead to mitochondrial dysfunction and the compensatory responses that precede it. Together, these findings could identify biomarkers of mitochondrial function and elucidate strategies to intervene at the earliest stages of dysregulation to prevent mitochondrial dysfunction and subsequent neurodegenerative disease.